an era

an era

Epoch, the starting date of chronology in history. The Chinese era began in the first year of the Republic of China in the Western Zhou Dynasty (841 BC). Since the first year of Jianyuan (140 BC) of Emperor Wu of the Han Dynasty, all the emperors of the past dynasties have established the era of the year, and some of them have changed the year halfway.

In Europe, the Greeks took 776 BC (the first Olympiad) as the era, and the Romans took 754-753 BC (the beginning of the construction of Rome) as the era. The Arab era is 622 ad (Muhammad moved from Mecca to Medina). Most countries in the world today adopt the year of the year ad.

Earth Era

Western ancient era

Other civilizations, such as the Greeks in 776 BC (the first Olympiad) as the era, the Romans in 754 BC to 753 BC (the construction of Rome) as the era, the Arabs in 622 BC (Muhammad moved from Mecca to Medina) as the era.

Ancient Chinese era

China's Kaokao era began in 841 B.C. (the first year of the Republic of the Western Zhou Dynasty), while the Xia Shang Zhou dating project pushed the Kao era to the history after Pangeng moved to Yin in 1300 B.C. Since the first year of Jianyuan (140 BC) of Emperor Wu of the Han Dynasty, all the emperors of the past dynasties have established the era, and some of them have changed their names halfway. Most countries in the world adopt the era of AD.

There are many dynasties in the history of China, each of which is ruled by different kings. From the Han Dynasty, the monarchs had their own year names, and each year name lasted from one or two years to several decades. Generally speaking, the division of geological age is from coarse to fine (of course, some emperors especially like to change the Yuan Dynasty, even twice a year. For example, 696 is the first year of "long live Dengfeng" and "long live Tongtian" under the rule of Wu Zetian. Don't pursue such extreme cases. They are just rough analogies.

Geological epoch

It is very difficult for us to accurately locate an event in human history to a certain point on a certain day. For similar reasons, we don't need to expect the geological age to be accurate to the year - it is not easy to define most periods within tens of thousands of years.

The largest unit of geological age is called "Zhou", which can be divided into dynasties, periods and epochs. Their corresponding strata or geological records are called universe, boundary, system and series. For example, a long winged dinosaur found in western Liaoning, China, lived in "Phanerozoic Mesozoic Cretaceous Early Cretaceous". Its stratum belongs to "Phanerozoic Mesozoic Cretaceous Lower Cretaceous" - when describing time, it uses "early, middle and late"; when describing space (stratigraphic sequence), it uses "lower, middle and upper". Further down, the time of maturity and maturity can be subdivided, and the corresponding strata are called steps and time zones, which are quite professional and rarely touched by non professional readers.

The name of Phanerozoic refers to the "age of visible life", which began in the Cambrian period 542 million years ago. In order to explain the distinction between Phanerozoic and previous ages, we must first focus on Cambrian. It was named in 1835 by the British geologist Sedgwick. It originated from Cambria in northern Wales where the strata of this period were discovered. The latter's name can be traced back to Cymry in ancient Welsh, which means "compatriots against the invasion of Anglo Saxons".

Cambrian was an important concept in the history of the earth before it was established as the official geological age: it was the earliest time when multicellular fossils were discovered. Later, multicellular animals before Cambrian were gradually discovered, such as the Ediacaran fauna that lived in present-day southern Australia more than 600 million years ago. The Cambrian period has also been re interpreted as the time when bilaterally symmetrical animals first appeared. The typical representative of such primitive animals is flatworms (worms have no bones or hard shells, of course they will not leave fossils, but their caves will become fossils).

In addition, an important event in the evolutionary history of the Cambrian "Cambrian explosion" occurred. In a very short period of time (geologically speaking, it was also millions of years), the species of organisms suddenly enriched and increased explosively. It means that in addition to gradual evolution, biological evolution may also take place in a jumping way.

With the name of Cambrian, the deeper and earlier strata are naturally called "Precambrian" strata. It is not a single period, but refers to all ages before Cambrian. In the 20th century, people used to call this period "cryptozoic era" (the age of hidden life), but it has rarely been used. The long period from the birth of the earth to the beginning of Cambrian (that is, before the beginning of Phanerozoic) is still called Precambrian. In addition to its end, the Ediacaran period, most of the Precambrian period has little to study, and there are no representative strata. Therefore, although it can be divided into Archean and Proterozoic, the boundary between the two periods, 2.5 billion years ago, is purely man-made, and the lower epochs, such as the iron forming period, the orogenic period, and the icing period, are also idealized, It is not defined by actual geological records. The age of the beginning of Archean has not been determined. Some people suggest that the period before Archean, which is as unpredictable as Hades and without life on the earth, should be called Hades. However, the term was not formally adopted in the 2004 geological year representative released by the International Commission on Stratigraphy (ICS).

In addition, before the end of Proterozoic and the beginning of Cambrian, there was also a Sinian period, which started about 800 million years ago. It is an important period for the development of life. The name comes from the ancient Indian name of "sunrise place" for China. In the new geological chronology, the period originally referred to by Sinian is basically replaced by glacial period and Ediacaran period.

Phanerozoic can be divided into Paleozoic, Mesozoic and Cenozoic, and the lower part can be subdivided into several periods. The names of these eras are most often associated with bizarre extinctions. From these names, it can be clearly seen that Britain was the center of early geology, especially in the Paleozoic Era: the names of Ordovician and Silurian came from the names of ancient Welsh people in Cambrian region, and the English name of Devonian is "Devonian", which represents the strata in Devonshire, England. The Carboniferous originated from a set of coal strata in England. The literal translation of Permian is "Permian". The strata are found in Perm city of Ural Mountains in Russia. The Permian is a free translation made in China according to the characteristics of strata. In the Paleozoic, ferns, fish and amphibians flourished. Then came the age of dinosaurs, the Mesozoic era, in which giant reptiles made their debut, including the Triassic, Jurassic and Cretaceous. Triassic is named after three sets of strata in southwest Germany, Jurassic is named after Jura mountain at the junction of Switzerland and Germany, and Cretaceous is named after the white fault wall formed by chalk soil on the English Channel.

In 65.5 million years ago, dinosaurs perished, and mammals that had lived in their shadow flourished in the Cenozoic Era and became the new rulers of the earth. The Cenozoic was originally divided into the tertiary and the Quaternary, which became the Paleogene and Neogene in the new chronology. It can be divided into seven epochs, from the earliest Paleocene to the latest Pleistocene and Holocene. In a word, one is more "new" than the other.

Era list

Hadean

3.8 billion years ago

Archean

Precambrian 2.5 billion years ago

Proterozoic

Late Precambrian: 570 million years ago

the paleozoic era

Early Cambrian: 564-535, Middle Cambrian: 535-515, late Cambrian: 515-500

Ordovician 500-436

Silurian 436-409

Early Devonian: 409-389, Middle Devonian: 389-378, Late Devonian: 378-360

Early Carboniferous: 360-335, Late Carboniferous: 335-284

Permian 284? - 242?

mesozoic

Early Triassic: 242-237, Middle Triassic: 237-229, Late Triassic: 229-208

Early Middle Jurassic: 208-159, late Jurassic: 159-140

Early Cretaceous: 140-94, Late Cretaceous: 94-64

Chinese PinYin : Ji Yuan